The present invention generally concerns a system and method for subjecting piezoelectric structures to the mechanical energy of conventional tire rotation, thereby generating electric power for integrated tire electronics. Piezoelectric technology is utilized to convert mechanical strain associated with tire flexure to electric charge that is then conditioned and stored in an energy storage device. Sufficient accumulations of such stored energy can then power electronic systems including components for identifying various physical tire parameters as well as radio frequency (RF) transmission devices.
The incorporation of electronic devices with pneumatic tire structures yields many practical advantages. Tire electronics may include sensors and other components for obtaining information regarding various physical parameters of a tire, such as temperature, pressure, number of tire revolutions, vehicle speed, etc. Such performance information may become useful in tire monitoring and warning systems, and may even potentially be employed with feedback systems to regulate proper tire pressure levels.
U.S. Pat. No. 5,749,984 (Frey et al.) discloses a tire monitoring system and method that is capable of determining such information as tire deflection, tire speed, and number of tire revolutions. Another example of a tire electronics system can be found in U.S. Pat. No. 4,510,484 (Snyder), which concerns an abnormal tire condition warning system. U.S. Pat. No. 4,862,486 (Wing et al.) also relates to tire electronics, and more particularly discloses an exemplary revolution counter for use in conjunction with automotive and truck tires.
Yet another potential capability offered by electronics systems integrated with tire structures corresponds to asset tracking and performance characterization for commercial vehicular applications. Commercial truck fleets, aviation crafts and earthmover/mining vehicles are all viable industries that could utilize the benefits of tire electronic systems and related information transmission. Tire sensors can determine the distance each tire in a vehicle has traveled and thus aid in maintenance planning for such commercial systems. Vehicle location and performance can be optimized for more expensive applications such as those concerning earth mining equipment. Entire fleets of vehicles could be tracked using RF tag transmission, exemplary aspects of which are disclosed in U.S. Pat. No. 5,457,447 (Ghaem et al.).
Such integrated tire electronics systems have conventionally been powered by a variety of techniques and different power generation systems. Examples of mechanical features for generating energy from tire movement are disclosed in U.S. Pat. No. 4,061,200 (Thompson) and U.S. Pat. No. 3,760,351 (Thomas). Such examples provide bulky complex systems that are generally not preferred for incorporation with modern tire applications. Yet another option for powering tire electronics systems is disclosed in U.S. Pat. No. 4,510,484 (Snyder), which concerns a piezoelectric reed power supply symmetrically configured about a radiating center line of a tire.
Another typical solution for powering tire electronics systems corresponds to the use of a non-rechargeable battery, which inherently provides an inconvenience to the tire user since proper electronics system operation is dependent on periodic battery replacement. Conventional batteries also often contain heavy metals that are not environmentally friendly and which present disposal concerns, especially when employed in highly numerous quantities. Still further, batteries tend to deplete their energy storage quite rapidly when powering electronic applications characterized by complex levels of functionality. Battery storage depletion is especially prevalent in electronic systems that transmit information over a relatively far distance such as from truck wheel locations to a receiver in the truck cabin. Even when batteries are used in electronics systems that transmit from wheel locations to a closer receiver location, information is then typically relayed via hard-wire transmission medium from the RF receiver location to the vehicle cab thus requiring the installation of additional and often expensive communications hardware in a vehicle.
Yet another known method for deriving power for tire monitoring systems relates to scavenging RF beam power with an interrogation antenna in close proximity to a tire and integrated electronic features. Energy that is radiated from the antenna is scavenged to power the electronics, which must often be very specialized ultra-low-power electronics limited to within a few microwatts. Interrogation antennas employed in conjunction with beam-powered electronics must typically be placed in relatively close proximity (within about two feet) to each wheel well due to limited transmission ranges. This typically requires multiple interrogation antennas per vehicle, thus adding to potential equipment costs. Each antenna is also quite susceptible to damage from road hazards, and thus for many reasons may not be the most desirable solution for powering certain tire electronic applications.
In accordance with the present subject matter, it is appreciated that certain advantages of piezoelectric materials have long been recognized. However, such technology is constantly improving, thus potentially affording applications that utilize piezoelectric materials with improved operating capabilities. Examples of relatively new advances in piezoelectric technology are provided in U.S. Pat. No. 5,869,189 (Hagood, IV et al.) and U.S. Pat. No. 6,048,622 (Hagood, IV et al.), directed to composites for structural control. The presently disclosed technology concerns further advances in piezoelectric technology such that a piezoelectric power generating device can be integrated with a tire or wheel assembly for purposes of energy harvesting.
The disclosures of all of the foregoing United States patents are hereby fully incorporated into this application for all purposes by reference thereto. While various tire electronics systems and power generation systems therefor have been developed, no design has emerged that generally encompasses all of the desired characteristics as hereafter presented in accordance with the subject technology.
In view of the recognized features encountered in the prior art and addressed by the present subject matter, an improved system and method for powering electronic systems integrated within a tire structure has been developed. Piezoelectric technology is utilized to convert mechanical strains associated with tire flexure to electric charge that is then conditioned and stored in an energy storage device. Sufficient accumulations of such stored energy can then power electronic systems including components for identifying various physical tire parameters as well as radio frequency (RF) transmission devices.
In accordance with more particular aspects of the disclosed technology, it is an object of the present subject matter to provide a pneumatic tire with integrated selfpowered electronic components. Such electronic components are self-powered by energy harvested from integrated piezoelectric structures, and may correspond with numerous electronic applications. One exemplary electronic application concerns a tire monitoring system designed to measure and transmit information regarding tire conditions such as pressure and temperature, as well as other information such as the number of tire revolutions or general tire identification variables. Another aspect of the related technology relates to methodology for generating energy to power such electronic devices.
Various features and aspects of the subject tire electronics system and specialized power generating device offer a plurality of advantages. The disclosed technology provides for a self-powered tire electronics system that is not dependent on replacement of batteries. Although batteries and battery-operated devices may still be incorporated with aspects of the present subject matter, many complications regarding tire electronics that are solely powered by batteries are obviated in accordance with the disclosed technology.
Another advantage of the present subject matter is that a tire monitoring system is provided that reduces the amount of required signal hardware relative to conventional tire monitoring systems. By providing a tire monitoring system that is self-powered, no scavenger antennas or multiple receiver locations with additional hardwire connections are required. Components of such a tire monitoring system can be integrated within each individual tire structure on a given vehicle such that a single receiver (typically located in a vehicle cabin) is capable of acquiring information transmitted by each tire""s integrated electronics.
Yet another advantage of the present subject matter is that there are fewer limitations regarding the type and amount of electronic equipment capable of utilization within tire and wheel assembly structures. Tire electronics powered by conventional methods other than as in accordance with the disclosed piezoelectric technology are often limited to ultra-low power devices. Devices in accordance with the disclosed technology are not necessarily subject to such extreme power limitations. This advantage further facilitates greater functionality of tire electronics, as more components and/or higher-level equipment may potentially be utilized.
A still further advantage of the present subject matter is that the disclosed system and method for generating power and utilizing such power can be used in accordance with a variety of existing applications. Measurement capabilities, monitoring and warning systems, vehicle feedback systems, and asset tracking potential may be possible for applications such as commercial truck fleets, airplanes, and mining/earthmover equipment.
In one exemplary embodiment of the present subject matter, a pneumatic tire assembly with integrated self-powered electronic components comprises a tire structure, an active piezoelectric fiber composite structure, a power conditioning module, and an electronics package. More preferably, the tire structure is characterized by a crown having an exterior tread portion for making contact with a ground surface, bead portions for seating the tire to a wheel rim, exterior sidewall portions extending between each bead portion and the crown, and an inner liner along interior crown and sidewall surfaces. The power conditioning module is electrically coupled to the piezoelectric structure to receive electric charge generated within the piezoelectric structure and generate a regulated voltage output. This regulated voltage output then powers selected components in the electronics package. The piezoelectric fiber composite structure and attached power conditioning module may be adhered to the interior crown surface of the tire or the piezoelectric structure could be cured directly into the tire""s architecture.
Another exemplary embodiment of the present technology concerns a tire monitoring system for integration with a pneumatic tire structure designed to measure and transmit information relating to preselected tire conditions. More particularly, such a tire monitoring system could comprise an active piezoelectric fiber composite, a power conditioning module, a plurality of sensors, a microcontroller, and an RF transmitter. The piezoelectric structure is characterized by a plurality of piezoelectric fibers embedded in an epoxy matrix and provided between at least two electrode layers, such embodiment preferably being either adhered to an interior portion of the pneumatic tire structure or mounted and cured within the tire structure itself. The power conditioning module is electrically coupled to selected electrode layers such that it receives electric current generated within the piezoelectric fibers and stores the current in an energy storage device until it is selectively provided as a regulated voltage output. The plurality of sensors are powered by the regulated voltage output and determine information regarding preselected tire conditions. The RF transmitter is electrically connected to and receives information from the microcontroller to modulate on a carrier signal and transmit to a remote receiver location.
A still further exemplary embodiment of the disclosed technology corresponds to a method for generating power from piezoelectric materials integrated within a wheel assembly. A first step in such a method involves providing an active piezoelectric fiber composite structure for incorporation within a selected interior location of the wheel assembly. Such piezoelectric structure is preferably characterized by a plurality of piezoelectric fibers embedded in an epoxy matrix and provided between active electrode layers. A next step in the method for generating power corresponds to subjecting the wheel assembly to mechanical strain generally occurring as the wheel assembly rotates along a ground surface resulting in flexure of portions of the wheel assembly and generation of electric current within the provided piezoelectric fiber composite structure. This generated electric current is then conditioned and stored in an energy storage device such that a regulated voltage source is available for powering electronic devices associated with the wheel assembly.
Additional objects and advantages of the present subject matter are set forth in, or will be apparent to, those of ordinary skill in the art from the detailed description herein. Also, it should be further appreciated that modifications and variations to the specifically illustrated, referred and discussed features and steps hereof may be practiced in various embodiments and uses of the invention without departing from the spirit and scope of the subject matter. Variations may include, but are not limited to, substitution of equivalent means, features, or steps for those illustrated, referenced, or discussed, and the functional, operational, or positional reversal of various parts, features, steps, or the like.
Still further, it is to be understood that different embodiments, as well as different presently preferred embodiments, of the present subject matter may include various combinations or configurations of presently disclosed features, steps, or elements, or their equivalents (including combinations of features, parts, or steps or configurations thereof not expressly shown in the figures or stated in the detailed description of such figures). Additional embodiments of the present subject matter, not necessarily expressed in this summarized section, may include and incorporate various combinations of aspects of features, components, or steps referenced in the summarized objectives above, and/or other features, components, or steps as otherwise discussed in this application. Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the remainder of the specification.